Auto-Focus while taking video at night with varying light.

Hi, I have a XMAS display synced to music on my house and tried to take a video of it tonight on my Nexus from across the street. There are lots of lights going off and on, from completly dark to rather bright throughout the songs. The Auto-focus will not stop adjusting when the ambient light goes from low to high. Constantly adjusting and ending up out of focus more often than not. Is there a way to turn off this auto focus feature inside the stock video app or possibly with an aftermarket one. I will even settle for a way to trick the camera to stop auto-focusing.